SETI: The Artificial Transit Scenario

by Paul Gilster on March 7, 2013

Among the many memorable things Freeman Dyson has said in a lifetime of research, one that stands out for me is relatively recent. “Look for what is detectable, not for what is probable.” This was Dyson speaking at a TED conference in Monterey, CA back in 2003, making the point that the universe continually surprises us, and by making too many assumptions about what we are looking for, we may miss unexpected things that can advance our understanding. Dyson has been thinking about this for a long time considering that it was way back in 1960 that he first suggested looking for the excess infrared radiation that might flag a distant Dyson sphere.

I would call this an unorthodox approach to SETI in its day except that when he first came up with it, Dyson didn’t have a SETI effort to consider. It was only in the same year that Cornell’s Frank Drake began SETI observations at Green Bank, and a scant year before that that Philip Morrison and Giuseppe Cocconi published the seminal paper “Searching for Interstellar Communications” in Nature. SETI in 1960 was a nascent field, but it would soon be focused on radio and, later, optical transmissions. Even so, Dyson’s thinking remains viable and unorthodox SETI efforts continue.

Image: Our Milky Way presents a field full of stars. How to search for signs of an extraterrestrial civilization among the countless targets? Looking for a Dyson sphere is unorthodox, but some scientists are suggesting this and other unusual ways of detecting the macro-engineering of distant civilizations. Image credit: NASA.

Luc Arnold (Aix Marseille Université) runs through the scholarship on what we might call ‘non-traditional’ forms of SETI in a new paper, noting that what he calls Dysonian SETI looks for signatures of macro-engineering projects in space. We’ve discussed many of these here before, delving particularly into the papers of Milan Ćirković and Robert Bradbury, but it’s worth recalling that others picked up on Dyson’s ideas earlier, including Carl Sagan and Russell Walker, who concluded as far back as 1966 that Dyson spheres should be detectable but would probably be hard to tell apart from natural objects having the same low temperatures.

In articles like Toward an Interstellar Archaeology, I’ve looked at Richard Carrigan’s searches for macro-engineering, and Luc Arnold reminds me in his new paper that Michael Harris has proposed methods of observing antimatter burning by advanced civilizations. Harris would go on in 2002 to use gamma ray observations in a first attempt to find such a signature. In fact, we can trace non-traditional SETI studies to authors as diverse as Ronald Bracewell, Michael Papagiannis and Robert Freitas, who along with several others Arnold references have followed Dyson’s lead in looking for what is detectable rather than what is probable.

Back to Arnold himself, who proposed in 2005 that transit studies like Kepler and CoRoT should be aware of the possibility of detecting an artificial signal. What the scientist has in mind is a planetary size object that orbits its star, constructed by a civilization as a celestial marker. The idea fits with something Jill Tarter said in 2001: “An advanced technology trying to attract the attention of an emerging technology, such as we are, might do so by producing signals that will be detected within the course of normal astronomical explorations of the cosmos.”

Transmission Methods and the Drake Equation

Arnold’s new paper compares radio wavelengths with laser transmissions and his own idea of artificial transits with respect to the factor L in the celebrated Drake Equation. L is generally considered to refer to the lifetime of a civilization, which obviously limits its ability to transmit a detectable signal. Working out the solid angle over which the transit could be ‘transmitted’ over one year, Arnold arrives at a figure of between 25,000 and 75,000 stars depending on stellar densities, and therefore uses a mean number of targets of 50,000 to set up comparisons between artificial transit ‘messaging’ and the more conventional radio and laser transmission options.

The idea is to examine efficiency as seen from the perspective of a transmitting civilization. A radio transmitter is the best choice for short-term messaging — a brief, highly targeted program of signaling — while lasers would require 102 times more energy. In terms of construction and maintenance, artificial transiting objects are more costly. They become interesting only for extremely long-term thinkers who are using the method to produce attention-getting signals where “…the transmitting time can be very long, possibly much longer than the lifetime on the civilization itself.”

Arnold notes that the shape of a transiting object shows up in the transit light curve, making the detection of an artificial planetary sized object a clear possibility. Weighing the costs and energy required to signal other stars, he concludes that if we make such a detection, it should be interpreted as the message of an old and perhaps defunct civilization. It would demonstrate at least that the lifetime of a technological civilization can be longer than several centuries.

It is also true that large artificial objects may be constructed for purposes other than communication. From the paper:

We may also argue that a civilization wanting to communicate with other beings also may want to leave a trace or an artifact in the galaxy that would survive much longer that the civilization itself. These two civilization behaviours seem not incompatible, but rather naturally linked and complementary, at least from an anthropocentric psychological point of view. But artificial planetary-sized objects may also be built for other technological purposes than communication, like energy gathering for example. Such macro-engineering achievements could be the result of natural technological evolution… making the will or desire of communication only an optional argument.

Arnold’s points are intriguing. SETI by radio and optical methods assumes we are looking for an active civilization. But lasers and radios fall silent when a civilization dies. Meanwhile, large artificial objects that transit their stars could remain indefinitely, markers of a culture that might have flourished billions of years ago and is now gone. The Dysonian approach of looking for macro-engineering thus offers the chance to do the kind of interstellar archaeology Richard Carrigan has championed through his exhaustive efforts. Turning up the signs of an artifact without any presumption of further communication still changes our view of the universe.

Who would construct a vast artificial occulter to send a signal to other stars? Several possibilities come to mind, including the idea that the occulting object might have been constructed for purposes other than being detected by another civilization. It is conceivable, though, that a dying culture would want to leave some trace of its existence. Because we are speculating on the motivations of extraterrestrials, we have no way of knowing. This is why Dyson’s idea of looking for what is detectable continues to resonate. Being surprised by the universe is part of our experience and there is no reason to expect that to change now.

The paper is Arnold, “Transmitting signals over interstellar distances: Three approaches compared in the context of the Drake equation,” accepted for publication in the International Journal of Astrobiology (preprint). Thanks to Antonio Tavani for the pointer to this paper.

hello Paul,
Fascinating concept. Is it true that you do not have to travel very far (relatively) from Earth for human engineering “artifacts” or signature achievements to become undetectable? That even non-directed radio waves can become hard or impossible to decipher?

I posted as as comment to Paul’s “Detecting a ‘Funeral Pyre’ Beacon” article back in Dec 2011:
“My first thought on how to make a very energy efficient beacon is to use the same occultation principle now used in Kepler’s planet hunting: Set up a bright “light” source and place several objects in orbit in it at various radii so that the pattern of occultations forms a meaningful message. ”

Another variation on this would be a Dyson sphere or ring in rotation with a series of “windows” in it that would allow the central star’s light to flash through it meaningfully when observed from afar. So, have we seen any cool brown dwarfs that seem to flare in a G or K type spectrum in a strangely regular pattern? Like this…

If we were to terraform Venus in our distant future, placing a solar shade at the Sun-Venus L1 point would be a likely first step. Conceivably other civilizations would look at terraforming of worlds that are too close to their parent star and have similar solutions.

A solar shade in that position would be very large. Perhaps it is possible to distinguish between the shade and the planet when watching the transit at a distant star.

“We’ve discussed that before,” said Truran Batten, from Vesta. “Whether our cooperation with quantum computers, and our MindCasts really makes us Human 2.0 or Human 1.5 or what.”
“It’s like interpolating on the Kardashev scale,” said Cossette.
“We have to assume that every civilization knows the Einstein equations, the Dirac equations, has measured parameters of Black Holes and Dark Matter in astronomical observation, and the equivalent of Turing Machines, in computation. Some of them develop quantum computers, but we don’t know what percentage. Some of them develop nanotechnology, but we don’t know what percentage. Some of them develop true artificial intelligence, but we don’t know what percentage. Some of them develop starships, but we don’t know what percentage. It’s a multidimensional Drake equation.”
“At the most naïve level,” said Emersona, “the civilizations that develop nanotechnology either gray goo themselves extinct, or become free from hunger and homelessness and other purely material economies of scarcity. The civilizations that develop quantum computers are able to solve hard problems faster, and may get to starships and true artificial intelligence sooner. The civilizations that develop true artificial intelligence get smarter, and may get to starships and nanotechnology sooner. It’s all very nonlinear, and hard to model.”
“Yet we know what seems to happen in the limit,” I said. “The hierarchical cosmos, with Kardashev I, II, III civilizations, in some sort of hard to decrypt communications with each other, engaging in planetary and stellar and galactic engineering.
“I’ve been trying to simulate all that,” said our cyb, “and so were my fellow AIs back in the solar system, but we never came to any certain conclusions. It seems to be fractal, in the percolation of starships carrying cultures physically through each galaxy. It seems to be chaotic, with arbitrarily small differences in what technology is implemented in which way at what time, leading to arbitrarily large differences in the capabilities of that civilization.”
“At least we’re not the very bottom rung of the ladder,” said Set. “Though there’s always the 20th century David Brin theory of Uplift, that we can make ourselves look better to our superiors if we help apes and dolphins and whales and so forth to true civilizations of their own.”
“It’s not an entirely benign picture that he painted,” said Tatiana. “We could end up enslaved by those higher on the Kardashev scale.”

The idea of a solar system, or interstellar scale monument is interesting. That might be beyond us for now. It reminds me of the Long Now Foundation (http://longnow.org/) who are building a clock that will run for 10,000 years. See: http://longnow.org/clock/. Of course that is at a much smaller scale, but it is a monument that will outlast its’ creators by a long time. It many not be found by anyone and if it is found it might be hard to interpret.

I think Dyson’s idea of looking for what can be detected instead of what we think should be there has parallels in the very current use of Big Data. The idea here is to collect as much data as possible and to search for any useful information afterwards. Very popular amongst advertising businesses like Google now.

As astronomical capabilities improve with new and better equipment being built, eg., ALMA, LOFAR and LSST and other space-based projects that cover large portions of the E-M spectrum I think we may well stumble onto some indications of a structure or processes of artificial origin. I could not attempt to guess what is probable but at least our detection abilities are improving greatly.

Ofcourse trying to determine if a set of anomalous observations were produced by an astrophysical event or by some example of alien engineering may provide material for years of vigorous debate. It would spur the development of a more powerful follow-up instrument to re-observe.

I really find it hard to believe that some alien civilization would make the huge effort to construct artifects just to signal their presence. Our purported neighbours would have built things for their own selfish uses only. But who knows for sure? Either way we should keep our eyes and minds open when analying the copious amounts of data generated by our current and future ground and space-based observatories.

Could there already be a discovery buried in some data base that no one has spotted yet?

Perhaps the sign of a truly intelligent and enlightened species is that they do not bother to leave monuments of any size to themselves for potential others. They know it is the mark not only of hubris, for even advanced beings that can build celestial-scale structures are still dwarfed by so much of the natural objects and events in both space and time of the Universe, but also that nothing truly lasts.

Think of all the monuments made by so-called great kings and their grand empires which are now gone to dust or ruins. Their few items that still survive into our time have only done so through deliberate and diligent effort by a relative few to preserve them. Think of the Buddhist tradition of those beautiful and elaborate sand paintings, which they subsequently brush away when finished. Their monks are saying nothing lasts, so enjoy life while you can. Anything else is vanity by minds that think they are the focus of a Cosmos they barely grasp.

So if there are massive structures in space and they do not serve a practical purpose such as housing a species or being some kind of vast platform for scientific instruments, does this mean we are seeing the efforts of an alien megalomaniac attempting to spread its self-perceived glory and intimidate weaker species?

The easy out is to say how can we comprehend what an extraterrestrial intelligence might do, but I do not consider it a stretch to say that no one would build something so big and so complex that it could be seen across the galaxy without a reason and the compliance of at least some of its members.

Since there are those who claim that the more technology advances the smaller our devices will get, not larger, then we would have to ask ourselves why would an ETI have a huge object or objects floating in space?

We already presume some degree of predictability – known stages to go through – in a development of civilization. I wonder if becoming preservation-minded is one of such expectable stages.

Think of a civilization already living to a great extent outside its home planet. Trough either direct or indirect exploration it finds (confirms) that rich biospheres are both relatively rare and unique in form on each planet they occur. This rarity and diversity might acquire a great value in the eyes of the civilization: you wouldn’t want to lose or seriously impair one lest it will be forever lost for the Universe. How likely is getting into such world-view?

Having the capability they, then, on the one hand, decide to move out from their home planet and establish a planet-wide wildlife reservation; nourish and guard it for the posterity to marvel on but never to live in. On the other hand, all the other accessible planets with rich biospheres if become targets at all then not for colonization but for protection (mostly from dangerous asteroids, I suppose).

But what does such preservation mindset implies from the large-scale artifacts point of view? Presumably it implies you don’t build anything massive enough to have unintended systemic gravitational consequences, including in the very long-term (those planet-size objects). It implies you don’t obstruct sunlight reaching the planet and thus no Dyson Spheres and only sparse enough Swarms between the planet and its primary. It implies you keep your footprint on the planet itself to the bare minimum. I’m sure there are more.

All in all, it implies downward pressure on the scale of your artifacts, at least in the inner system, wherever you have a planet with complex life. Thus making the artifacts harder to detect in those places and perhaps moving the real large-scale structures further out and into biologically bare systems.

After reading the article I’m not sure if I agree with what Dyson says or not.

He says we should search for ‘what is detectable’ and then that we shouldn’t make too may assumptions about what we are looking for, we may miss unexpected things. I don’t think you can have it both ways. Right now we only have two ways to detect anything – RF and optical. We choose these two parts of the EM spectrum by making assumptions about what could be sent and what we are able to receive. We really have no other choice.
This is my take on it:http://www.seti.net/SETINet/Other/Reading/Looking%20For/Looking%20For.htm

An Orbital would have a slight tilt (to provide a day/night cycle) that may produce some interesting effects but compared to their diameters, they’re thin. Just guessing:

I think there may be some differences if the Orbital is perpendicular to its orbital plane, (so it looks like a long, narrow vertical bar crossing the star) vs almost coplanar with only a small inclination but I can’t think of what the differences would be, other than timing. The vertical Orbital might show a sharp drop in the light curve, a deep minimum then a sharp return as it exits. Maybe with some diffraction effects if enough starlight makes it through the central gap. The almost coplanar Orbital would have a smaller but longer drop, also (hopefully) with some diffraction effects.

It might be difficult to distinguish from just a very big planet, but the depth and length of the eclipse may point to an impossibly massive planet (ie, a star sized object, but dark and not as massive as a star). Orbitals are supposed to be about 3 million km. in diameter x several thousand thick, so we’re talking a good sized occulter.

If interstellar travel is possible, then the Drake equation is meaningless, since the locations at which intelligent life exists will then be overwhelmingly colonies, not sites at which intelligence first evolved.

Dyson’s approach ought to be considered common sense. We have no reasonable expectation that any alien civilisation is deliberately messaging us, because (as Paul Davies has pointed out) no such civilisation can be aware of our existence, unless they are already in the Solar System. But we can expect that if those civilisations exist, one possible route of development would be to produce macro-engineering constructions observable at interstellar ranges.

Instead of building something so gigantic that its anomalous electromagnetic emissions could be detected across the galaxy, it might be possible to instead “modify” existing astronomical objects so that the changes–which would be of such a nature that they could *only* be artificial–would be detectable from anywhere (except from behind dense dust clouds) in the galaxy. If civilizations are rare in the galaxy, such a project could even be an act of charity by a civilization that instituted it, a statement to other races that “*You* are not alone!” Now:

In “The Promise of Space,” Arthur C. Clarke suggested that an advanced civilization could “label” its sun by dumping into its atmosphere vast quantities of artificial elements that do not exist in nature, so that the “label(s)” would appear in the star’s spectrum; he added that “in some cases, the amounts of matter needed would be a few hundred thousand tons–not an unreasonable figure.” The artificial elements might even be waste products from Earth- or space-based industrial processes. Moon-based electromagnetic launchers could project the material into our Sun by firing the projectiles out toward Jupiter, which would cancel out their solar orbit velocity so that they would fall into the Sun.

If we’re talking about signaling via mega-engineering, doesn’t a variation on a Dyson “swarm” make more sense? Build every free-flying component to (1) be flat and thin; (2) have an on-board gyroscope, allowing rotation between “face-on” and “edge-on” aspects; and (3) have self-repair capability. (Points 2 and 3 already seem necessary for a solar-powered Matrioshka brain, anyway.) Then the entire swarm could pull a coordinated “venetian blind” maneuver, generating an omnidirectional signal of arbitrary complexity and stellar brightness.

Finding the other intelligent lifeforms in our local galaxy is a bit of a chore. Considering the predictions of what is to come; Andromeda and the Milky Way are on a collision course in 2 billion years… we should try to scan the intergalactic medium for travel activity? And we are definitely going to send probes within the next million years. Do long term technical civilization actively pursue such enterprises? We can’t even get a sound policy toward an asteroid management program.
Finding alien civilizations would tells us one thing; intelligence has long term survival value.

Furthering D. Ibekwe’s idea, a super advanced ETI may not only have the Kardashev horsepower to place massive objects in certain orbits around stars or planets, but they may have a hold on physical reality itself.

So what I am proposing is a metric analogous to the Kardashev scale that measures an ETI’s ability to manipulate space-time and other physical constants like the cosmological constant. This would be evidenced by anomalous observations in, say, for example, orbital parameters or planetary arrangements that just don’t make sense to us by defying what we know of our local physical world.

They may be fine-tuning their biosphere by keeping their home planet in the same classical orbit but moving twice as fast as Keplerian/Newtonian physics allow. Or, with an homage to Contact as a possible message to others, it might orbit 3.14 times slower.

These examples are regarding gravity at least, but they extend to ‘c’ and even the forces such as the weak force, etc… And since all these constants are so intertwined and fine-tuned, the scale is possibly logarithmic, as well.

“If civilizations are rare in the galaxy, such a project could even be an act of charity by a civilization that instituted it, a statement to other races that “*You* are not alone!”

Charity for who really? Would such an ETI really want to “comfort” some unknown (and potentially dangerous) alien species? Or is it to make them feel better about being alone in a big, scary Universe?

Again, however, we are putting human assumptions and behaviors on an alien species. Which it is also clear they are assumed to be organic too. They could be quite content (and safe) in their little corner of the galaxy with no intention or need to contact others. Indeed, if they are so advanced, primitive emotions like fear may not exist for them.

If they understand the Universe better than humans do – and by that I mean truly appreciating what things are like in existence and their place in it – then perhaps they do not spend their time and energy trying to figure out their purpose, the meaning of life, and so forth.

“Finding the other intelligent lifeforms in our local galaxy is a bit of a chore. Considering the predictions of what is to come; Andromeda and the Milky Way are on a collision course in 2 billion years… we should try to scan the intergalactic medium for travel activity? And we are definitely going to send probes within the next million years. Do long term technical civilization actively pursue such enterprises? We can’t even get a sound policy toward an asteroid management program.”

That is an interesting thought, to send vessels to the Andromeda Galaxy as it gets closer. Or maybe the residents of that stellar island will send probes to their new much closer neighbor, too. Though I doubt we will be around at least in our current form to do such a thing ourselves, so we better hope someone else is inspired about the idea.

Still, if Andromeda is about one million light years from the Milky Way galaxy and FTL methods have not yet been invented or found, would it make sense to send a probe that will take so long just to get there? And then require over a million years to send back any messages or information? or someone still might send one as a gesture of intergalactic goodwill or whatever, but it won’t be very practical scientifically.

“Finding alien civilizations would tells us one thing; intelligence has long term survival value.”

Only if they are similar to us and developed as we have. Otherwise something like a gasbag floating in a Jovian atmosphere or a blob of plasma living deep inside a star or an Artilect would only mean that their kind can make it. Humans have yet to prove they can colonize their nearest Sol system neighbors or keep their recently technological society from collapsing upon itself either by external or internal forces.

Kepler has shown us that planetary systems containing MULTIPLE tansiting panets are VERY COMMON! ET’s would know that we know this as well! Therefore,one thing to look for would be four transiting objects,A<B<C< and D, with the following ORBITAL PERIOD RATIOS: B to A equals PI, Cto B equals e, and D to C equals PHI! This would BOTH; Prove the ARTIFICIALLITY of the system, AND , convey INFORMATION similar to information we might expect from a radio signal!

There could be very strong observational constraints on Dyson Spheres – possibly stronger than anything else in SETI. It was mentioned that WISE telescope could detect 300K-free-flying super-jovians at several ly. A point object radiating in thermal IR with bolometric luminosity of a main sequence star would be visible at the halfway to the other end of the galaxy distances. And if the Matrioshka Brain is capable of interstellar colonization, one could suppose it would target O-B-stars to obtain maximum power for computation – these monster swarms would show up through all the Local Cluster (and be blazingly bright in IR if located in our own Galaxy). A spectre full of super-narrow laser lines in the near IR and visible ranges, indicating high-bandwidth intra-brain communication, would be the telltale sign…

Meanwhile, large artificial objects that transit their stars could remain indefinitely, markers of a culture that might have flourished billions of years ago and is now gone.

I really find this notion of “civilizations that are long gone” extremely implausible. The property of self-replication makes life practically eternal. Our planet has been inhabited continually for several billion years, with no end in sight. If interplanetary and interstellar travel eventually spread life beyond our planet, there is nothing that could eradicate it.

The Roman Empire does not exist anymore, but it has been replaced by a thriving modern state. The population of Rome is orders of magnitude higher, today. Hardly a “decline”. The ruins are hard to find not because they have decayed, but because they have been paved over a hundred times. In 10,000 years, it is far more plausible that Earth will resemble Asimov’s Trantor, than for humanity to become extinct with nothing but ruins left.

railmeat:

It reminds me of the Long Now Foundation (http://longnow.org/) who are building a clock that will run for 10,000 years. See: http://longnow.org/clock/. Of course that is at a much smaller scale, but it is a monument that will outlast its’ creators by a long time. It many not be found by anyone and if it is found it might be hard to interpret.

I don’t think that this is the idea. The idea is that the clock will be visited regularly and wound manually. It is my understanding that the clock will stop if not wound, and that the intention is to keep it well wound and running throughout the entire 10,000 years. An “inherent statement of optimism”, as it is put somewhere on the site.

In keeping with my first comment above, I do not think that the clock will be forgotten and “found by anyone” later. It is far more likely that it will become a long-time tourist destination, regularly visited and wound by Martian colonists 10,000 years from now. Not unlike the Coliseum in Rome, the Acropolis in Athens, the pyramids in Egypt, or the Great Wall of China, which all have visitors from The New World swarming around them every day.

[Charity for who really? Would such an ETI really want to “comfort” some unknown (and potentially dangerous) alien species? Or is it to make them feel better about being alone in a big, scary Universe?]

I have no idea of what motivations aliens may have. Other posters suggested that alien races building such conspicuous works of engineering intended to be seen by others would be doing so out of hubris; I merely suggested a more honorable possible motivation, especially if the civilization in question *knew* that intelligent life was rare and had reached a level of wealth and stability to make such projects practical.

[Again, however, we are putting human assumptions and behaviors on an alien species. Which it is also clear they are assumed to be organic too. They could be quite content (and safe) in their little corner of the galaxy with no intention or need to contact others. Indeed, if they are so advanced, primitive emotions like fear may not exist for them.]

I make no assumptions about what forms and behaviors aliens may have–including whether they are physical or not; as the late Patrick Moore was fond of saying, “We just don’t know.”

[If they understand the Universe better than humans do – and by that I mean truly appreciating what things are like in existence and their place in it – then perhaps they do not spend their time and energy trying to figure out their purpose, the meaning of life, and so forth.]

That goes right back to the charity possibility; although it is certainly not a given, I would not be at all surprised if a civilization that had “figured it all out” might–especially if it knew that intelligent life was rare–feel motivated to help an up-and-coming civilization reach its level of understanding. It could “disarm” (in the philosophical sense) a potential enemy via peaceful means, while also “creating” an interesting neighbor to talk with and exchange insights with. Or they might ignore–or want to destroy–the young whipper-snappers instead; we just don’t know.

Joke aside SETI should search for debrises of an exploded planet in HZ or near the edges. This would be clearly detectable in star transit spectra. By detecting such feature it means there are ETIs, more than one (foe and enemy) and no less than two (destroyed foe on the planet). Regard this like a Death Star in Star Wars destoying a planet which indicates a Kardashev II-type civilisation annihhilated another civilisation.

So, that would mean we are not alone and there are others. At least one of them is active (in case they are not extinct by the time). This discovery would resolve the issue of executing the Respond Protocol.

It also could be a natural phenomenon like rouge hypervelocity planet colliding with another solar system planetary celesital body but that would mean insterstellar jackopt anyway.

The search for waste heat from alien civilizations can be thought of as a form of artifact SETI. That is, instead of looking for the signals of alien civilizations, we look for physical evidence of their existence. This could be markers scattered throughout the Solar System, crash-landed spacecraft, or, of course, parts of Dyson spheres. Richard Carrigan calls searching for such things “interstellar archaeology”.

A “partial” Dyson sphere would periodically eclipse or transit its host star, creating distinctive photometric signatures. Geoff Marcy is looking for such signals in Kepler data, and my search for waste heat is looking for the glow of these mega-engineering projects.

A provocative and smile-inducing paper was published by Luc Arnold that investigated Kepler’s ability to find such things. Arnold’s angle was actually at the border between artifact SETI and traditional communication SETI.

Arnold first pointed out that Kepler would be able to distinguish between spherical planets and other shapes — say, triangles — if the transit signal was strong enough. He argued that artificial objects the size of planets placed in orbit around stars would have a low-baud-rate but be fantastically efficient — essentially you would get around the problem of how find the power to communicate over very large distances by using the star itself as your beacon.

It’s a brilliant idea: you don’t need to collect the power of your star to use it to power big radio transmitters, you just need to block enough of it that other civilizations notice it flickering, and you’ve essentially got a one-solar-luminosity transmitter!

Clearly, the message here is that a “cheap” way for aliens to attempt communication would be to build these devices that might last for a very long time with little maintenance and send signals visible across the Galaxy. We should always be on the lookout, it follows, for transits from planet-sized objects with highly variable depths. After all, it would be very difficult to come up with any natural explanation for such a phenomenon (*ahem*).

Which brings me to KIC 12557548, a bizarre star in the Kepler field of view with an apparently transiting object whose eclipse depths vary by a factor of six (sound familiar?).

The authors go to valiant lengths to find a natural explanation for this, and come up with a Mercury-sized object that is evaporating, and the cometary cloud behind it has turbulence that generates highly variable opacity to the starlight.

Now, I don’t know what this is. Maybe it really is an evaporating planet (the best guess, I’d say). Maybe it’s KH15D all over again, but with some high-frequency twist of some kind. I’d bet my house on it not being aliens.

But given that he went way out on a limb and predicted almost exactly this sort of thing, don’t you think Luc Arnold at least deserved a citation?

(To be fair, I should be generous and assume that the authors weren’t aware of Arnold’s paper. But I’m not at all sure they would have cited it if they had. And, who knows?, perhaps the referee wouldn’t have taken it seriously if they had.)

“The Roman Empire does not exist anymore, but it has been replaced by a thriving modern state. The population of Rome is orders of magnitude higher, today. Hardly a “decline”. The ruins are hard to find not because they have decayed, but because they have been paved over a hundred times.”

This is all true. The difference as I see it between the fall of the (Western) Roman Empire and the subsequent decline and eventual rise to a modern technological state and any future collapses of our current civilization is that I wonder if we will be able to recover enough from such a disaster beyond some form of medieval level existence – assuming we would survive outright extinction.

Our distant ancestors knew how to hunt and farm and build their own houses. How many can say that today, especially in the more developed nations? Even more importantly, even if there were enough people with those basic skills available, would there be enough resources to build ourselves back up this time? Would pollutants such as from abandoned chemical and especially nuclear power plants hamper things even further? I have yet to see a mainstream post-apocalypse film or series address this issue, but if our nuclear power plants are left unattended, the fuel rods would overheat and cause serious radiation leakage, spread even further by the winds and lasting for decades or more.

There is always this romantic fantasy of hardy people surviving a nuclear holocaust or a global pandemic or a major impact from space and eventually building back up to exceed our current level of existence. Even one of my favorite SF novels, A Canticle for Leibowitz, imagined humanity reaching for the stars a mere few thousand years after a nuclear war, one where the survivors not only destroyed any remaining technology but killed anyone with scientific and technical skills they could find and eventually went after anyone who could even still read.

So yes, life may go on, but it may not go anywhere, particularly to colonize another star system. Even without a major disaster to contend with, note how much of modern civilization is not devoting even a significant portion of its money and resources to space utilization. Newt Gingrich’s mere suggestion of a permanent manned lunar colony during last year’s US Presidential campaign was met with derision by both sides of the political spectrum. I have trouble imaging a society reduced to a Stone Age level of existence caring or knowing about a mission to Alpha Centauri any time soon, if ever.

I know that there may be ETI which might do better than us and succeed on all sorts of levels, but at the moment they remain hypothetical.

Eniac then said:

“In 10,000 years, it is far more plausible that Earth will resemble Asimov’s Trantor, than for humanity to become extinct with nothing but ruins left.”

Would a Trantor-style civilization, one that covers most if not all of the planet, be good for Earth and humanity? Would we be able to sustain such a world? Would it simply make more sense of colonize space, since such a society would need the resources of other worlds to maintain so much high technology and so many people.

By the way, Asimov preferred to spend his days and nights indoors. His Trantor residents liked living underground in artificial environments. I recall one minor character saying he had not even been outdoors in years and could not understand the appeal.

Maybe Asimov liked staying inside, but I know of plenty of people who would literally go crazy if they had to live that way. I am not outdoorsman, but I like looking out a window now and then and breathing (relatively) fresh air and having actual sunlight on my face over fluorescent lighting.

And if you have a whole society that prefers to be inside a building, how many of them are going to be looking at the stars and wanting to reach them? Already artificial light pollution is ruining night skies all over the planet and not just in urban areas.

My fervent hope is that even if FTL travel is impossible or wildly impractical, the next major technological revolution will be some kind of superluminal communications, based on quantum entanglement or the fabled “hyperwave.” If either is remotely possible, they would probably be achievable soon – say within the next century or two, which would put a new spin on the Fermi Paradox: if a civilization goes from blasting RF to completely silent because of better means of communication within a few centuries, that would certainly explain the quiet out there. In which case, yes, if any civilization wants to be or doesn’t care if it is detected, it would have to be from obvious artifacts or deliberate displays.

“Gingrich’s idea was laughed at because he wanted it accomplished within a ridiculous time frame, 8 years, when there isn’t even hardware available to land a crew on the Moon for a short term visit.”

That was only part of it. He may also have been echoing NASA’s earlier plans, which talked about putting a permanent base at the lunar south pole by 2020.

Most people just found the idea itself ridiculous, a huge step backwards from our visions of the early Space Age. Mitt Romney infamously said he would fire anyone who came to him with such an idea, so you can imagine how poorly NASA would have fared under his rulership. Just about every other candidate from 2012 also ragged on Gingrich’s comment because it had to do with space and so many of the sheep went along with it.

How will this bode for us making an interstellar mission possible? It does not help when the focus on the last 100 Year Starship conference was on warp drives and other fantasies.

It is perhaps worth mentioning a fact that is not well known, but quite interesting. Mainly that we did perform searches for Dyson Spheres before…And candidates were found. However they can’t be confirmed(17 candidates were found in one search)

Is anyone ever going to follow up on these potential Dyson Shells? The edge-on spiral galaxy NGC 5907 also needs to be investigated further for supposedly having a higher amount of red dwarfs than normal for a galaxy of its type and age.

Current SETI is not that expensive. Dr. Stuart A. Kingsley showed in 1991 that experienced amateur astronomers could do real Optical SETI and no doubt the technology has improved and the expense has dropped since then. The SETI League’s idea of thousands of serious amateur radio astronomers all across the globe conducting SETI is a good one, but they only have a handful of people monitoring these days.

Would a Trantor-style civilization, one that covers most if not all of the planet, be good for Earth and humanity? Would we be able to sustain such a world? Would it simply make more sense of colonize space, since such a society would need the resources of other worlds to maintain so much high technology and so many people.

I am not sure if you meant to imply it, but colonizing space will not slow population growth on Earth, why should it? Earth’s population, of course, will be limited one way or another. Once humanity expands into space, this will be a local problem, with mostly local solutions. The future of humanity will no longer depend on solving it.

By the way, Asimov preferred to spend his days and nights indoors. His Trantor residents liked living underground in artificial environments. I recall one minor character saying he had not even been outdoors in years and could not understand the appeal.

Maybe Asimov liked staying inside, but I know of plenty of people who would literally go crazy if they had to live that way. I am not outdoorsman, but I like looking out a window now and then and breathing (relatively) fresh air and having actual sunlight on my face over fluorescent lighting.

Asimov was indeed one of the many Manhattanites who have very little desire to go elsewhere. I think Woody Allen is another famous example (although he seems to like Paris, too). I would be willing to bet that if you sent Manhattan into space, a large part of the population would easily deal with it. Provided you could do it without undue interruption of city services and while keeping the Korean owned corner groceries well supplied…..

I find the notion of green fields, lakes, hills, villages, etc. on the surface of a giant artificial structure quite absurd. It would never happen. Space structures will be like buildings. It is how we live, most of us, already. Does anyone really think that being deprived of the few days per year we may go out camping in the wilderness will drive anyone nuts? Not me.

“I am not sure if you meant to imply it, but colonizing space will not slow population growth on Earth, why should it? Earth’s population, of course, will be limited one way or another. Once humanity expands into space, this will be a local problem, with mostly local solutions. The future of humanity will no longer depend on solving it.”

No, I was not implying that. I was referring to the fact that you said Earth would become like Trantor, which means massive amounts of artificial structures covering the planet (I forget, did Asimov’s world cover the oceans, too? Or did they just drain them first?). I am saying I doubt such a technological society could exist if it were meant for biological creatures.

They would eventually have to get their resources from beyond Earth. That would be quite expensive, plus one has to wonder how long space colonies would want to keep sending supplies to the old nest and what terrans would have to offer the spacers to keep them invested in doing so?

Eniac then said:

“I find the notion of green fields, lakes, hills, villages, etc. on the surface of a giant artificial structure quite absurd. It would never happen. Space structures will be like buildings. It is how we live, most of us, already. Does anyone really think that being deprived of the few days per year we may go out camping in the wilderness will drive anyone nuts? Not me.”

Yes, I actually do think that many people would go crazy, both literally and figuratively, if they were denied green grass, trees, big bodies of water, etc. There is a reason why a good chunk of very expensive Manhattan real estate is taken up by something called Central Park.

To get “nature” out of humanity you will have to change our species to the point that it will no longer miss such things as the outdoors, or at least not need it on a physiological level. Then we will no longer be human. Whether you find that to be a good or bad thing is relative.

Next, we will be putting the forests into domes and launching them out towards Saturn….

@ljk March 14, 2013 at 13:57
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[Current SETI is not that expensive. Dr. Stuart A. Kingsley showed in 1991 that experienced amateur astronomers could do real Optical SETI and no doubt the technology has improved and the expense has dropped since then. The SETI League’s idea of thousands of serious amateur radio astronomers all across the globe conducting SETI is a good one, but they only have a handful of people monitoring these days.]
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ljk, you are on right track. I was pondering same thing when read Mike Brown’s Planets blog of Kupier Belt Objects. The nowadays cost of radio and visual astronomy with devices for consumers in such variety is question of collaboration and willingles of investment. Also the aura of doing astronomy is still shrouded with notion of being elite or especially gifted person undermining ordinary laymans who might have interest for it – no-life kids, retired persons, housewifes, ordinary / curious people, working person who challenge itself, just for fun – even if for a time being. Yet even in such citizens astronomy and crowdsourcing era its still is scattered, high entry barrier, too steep, long, and wide learnign curve.

Enorumous amount of astronomy is done on data mining / analysis / statistical calculation. Diversity what crowdsourced citizens astronomers might bring could be steered emphasizing quality of equipment and data acquisition. The tip should be on citizens astronomers willingness to pariticapte no matter how big or small or short.

* Some might want to install equipment and provide astronomy time.
* Some might want to provide useful knowledge.
* Some might want to help spreading the work and understanding.
* Some might discover their powers helping on something they can provide (inside, innerthinking, eagle eye on mismatches, etc.

* If there would be a thousand citizen astronomers devices online for observation and data acquisition over the world , fully automated, ready per request, that would benefit significantly. There is just not enough timeslots for professionals.
*Advances in OpenSource hardware and software design and automated observation equipment would improve significantly in both ways – professional grade design emerges on amateur side, also amateurs with testing different technical proof of concepts will shorten maturity-to-market time. For instance can’t comprehend why atmospheric perturbation correction technique is not (yet?) available for amateur astronomers.
* The extent of available data per event, per date or per any necessary timeframe will increase, thus increases chance to understand events via acquired data.

But the hard thing would me make it connect. The resistance would not be on the citizens side, it will be on the professional side who will most likely reject it and make all in power not to happen. This is normal way of things evolve. Also there must be a framework to carry on and support of small groups of professional side. Take it like a Mozilla Community for astronomy.

It will never happen if the idea will be formulated on vague someone, somehting, somehow, someway level.

Formulating the framework would never be a problem. The hard questions is who and how will proceed w/ it.

I was perplexed it took Mike Brown two decades from observation, data processing, and making discovery, to say that no-one else had looked at Kupier Belt thoroughly and there is a lot of unknown awaiting. This is just too long. It’s your backyard.

An example of crowdsourcing by ESA to improve data generation for future automated space docking vehicles. ESA Parrot quad-drone which could be steered via iPhone (no Android support) allows collect the camera recording data what the player sees on the iPhone and send to ESA to analyse variations and determine the best algorythms.

“I am not sure if you meant to imply it, but colonizing space will not slow population growth on Earth, why should it?”

Well, I think if the Earth only had a few million people visiting it at a time then that would certainly qualify as slowing population growth.

A beam propulsion system is the likely system (the only likely system IMO) to provide an airliner to space. Building habitats that are so much safer and more comfortable than living on Earth would start a mass exodus. Why not?

“Silent Running would have been more believable if it had used habitats that would spin for artificial gravity and had shielding against radiation.”

Silent Running would have been more believable if it did not indicate that Earth’s biosphere was essentially gone and yet somehow the human race not only survived this catastrophe but enjoyed and thrived in their new artifical conditions, with only a few wild-eyed dissenters ranting and raving to the annoyance of the rest.

And using nuclear bombs to destroy the biodomes? Talk about excessive, especially in the symbolism department.

I found the following article about perhaps detecting artificial lighting on exoplanets / exomoons very interesting and in the Dysonian SETI spirit in that such civilizations would not necessarily be intentionally transmitting a signal for our detection but rather they, like us, would do it as a result of them using artificial lighting for various purposes.

About detecting ETI via the lights of their cities: Would that be a sign of intelligence or a lack thereof that they conduct artificial light pollution on such a massive scale that it can be seen for light years?

Light pollution is taking away the stars on this planet, giving more and more people fewer reasons to want to reach for them. Will this be the case for an alien technological civilization that also feels the need to circumvent the natural day-night cycle for primitive reasons?

It’s a disturbing question, and one that I seem to get more frequently than before.

“Why are you looking for evidence of extraterrestrials? What’s the point?”

While I have always thought that the motivation for looking for E.T. was both self-evident and patently worthy, it’s possible that I’m a victim of my own job description. Others don’t inevitably agree. Some will opine that there are better ways to spend the money.

That’s the same argument that’s often lobbed at NASA’s space programs, and at basic research in general. The thrust is that if your work isn’t obviously helping to better my lot (or maybe the lot of a lot of others), then you’re just friction in the system.

My knee-jerk rejoinder to this all-too-easy humanism is to note that the amount of money involved is tiny. The total funding of SETI (the Search for Extraterrestrial Intelligence) in the U.S. is 0.0003 percent of the tax monies spent on health and human services. And it’s not even tax money. The SETI Institute’s hunt for signals is funded by donations.

But while pointing out the realities of funding is certainly legitimate, I’ve recently promised myself to avoid doing so. It gives up too easily, and sounds like a confession: “Yes, you’re right. It’s a waste, but a very small waste.”

Well, it’s not a waste. The hunt for other sentience in the cosmos is done for reasons that could be extremely important and that, in any case, gratify the finest aspects of our spirit.

Consider the practical consequences of discovering company among the stars. These benefits are, admittedly, uncertain and hard to predict. They depend on whether we could ever decode signals from intelligence that is not only many light-years distant, but enormously ahead of us in technical ability. We’re not going to hear from beings that are at our level – they won’t have the equipment necessary to transmit a signal that today’s SETI experiments could pick up. So if a radio disturbance from ET someday floods our antennas, you can be sure that whatever’s behind the microphone would judge our own knowledge of science to be merely quaint.

Consequently, if we can make heads and tails of their signal, we could become privy to knowledge that would otherwise remain unknown until developed by our descendants centuries or more in the future. While this manna from the skies could be profoundly disruptive, you can’t argue that ignorance is blissfully preferable. It’s not.

But what if – as is thoroughly possible – we’re unable to understand ET’s broadcast? What if we just know they’re there? In the months following a detection, intense study of the signal source would garner a handful of astronomical facts – the distance to the senders, a few planetary parameters such as the length of day and the likely mean temperature, and possibly some information about the atmosphere. All of which would be interesting, and even mildly informative (did ET evolve on a world somewhat like our own?) But it would leave us guessing about the inhabitants based on the habitat. And the meaning of the message might eternally elude us.

However, even without that prize, the contest is more than worthwhile. Exploration is an oft-lauded human activity, and one that resonates in the same way that music and good stories do. It’s hard-wired into our species (and into many others), no doubt because it has survival value. Exploration occasionally rewards those who accept its risks, usually with new resources.

There’s little need to expound on the romantic lure of exploration, for few would dispute it. But there’s a special appeal in a search for other-world intelligence. We have a deep fascination for this because, after all, Darwinian mechanisms ensure that all life has a paramount interest in its own species. For us, other thinking beings are subconsciously regarded as potential equals, and interest us as competitors or mates. Of course, real aliens would be neither, but their sentience makes them compelling in a way that extraterrestrial bacteria are not.

Our curiosity is broader than merely the innate interest in cosmic doppelgangers, however. We want to know if intelligent life is some sort of wildly improbable accident. Are we the only members of the Galaxy that can actually understand what a galaxy is? Could Homo sapiens really be the pinnacle of Creation – the cleverest critters in the cosmos? If we learn the answer is “no”, that would affect our philosophies forever.

In the past I was seldom asked why we hunt for extraterrestrial company, only how. Perhaps the realities of today’s world have narrowed our vision to the near-to-hand. SETI is too speculative. And sure, concern for the immediate and the demonstrably practical is helpful in the short-term. But if we only look nearby, we can’t see where we’re going.

Frank Borman remarked that “exploration is really the essence of the human spirit.” Borman’s an astronaut, so he was tipping his hat to his own career. And so am I when I say that SETI is done out of curiosity, and is both tremendously exciting and undoubtedly worthwhile. It might alter the trajectory of our civilization. But more than that, a search for others feeds the best in our nature.

It’s a big galaxy out there. Even the most skeptical scientist has to accept that if a civilisation like our own exists, then there’s a good chance we’re not the only one to have ever done so.

When most people think about SETI (the search for extraterrestrial intelligence), they imagine someone like Ellie Arroway searching the skies for radio transmissions. But what about looking in other ways? Perhaps a highly advanced alien civilisation might build structures large enough for us to see.

An idea that really captures my imagination is what kinds of future civilizations there might be. And I’m not the only one. In 1964, the Soviet astronomer Nikolai Kardashev defined the future of civilizations based on the amount of energy they might consume.

A Type I civilization would use the power of their entire planet. Type II, a star system, and a Type III would harness the energy of an entire galaxy. It boggles the mind to think about the engineering required to rearrange the stars of an entire galaxy.

Is it possible to move a star? Could we move the Sun?

This idea was first proposed by physicist Dr. Leonid Shkadov in his 1987 paper, “Possibility of controlling solar system motion in the galaxy”.
Here’s how it works.
A future alien civilization would construct a gigantic reflective structure on one side of their star. Light from the star would strike this structure and bounce off, pushing it away.

If this reflective structure had enough mass, it would also attract the star with its gravity.

The star would be trying to push the structure away, but the structure would be pulling the star along with it.

If a future civilization could get this in perfect balance, it would be able to “pull” the star around in the galaxy, using its own starlight as thrust. At first, you wouldn’t get a lot of speed. But by directing half the energy of a star, you could get it moving through the galaxy.

Over the course of a million years, you would have changed its velocity by about 20 meters/second. The star would have traveled about 0.3 light years, less than 10% of the way to Alpha Centauri. Keep it up for a billion years and you would be moving a thousand times faster. Allowing you to travel 34,000 light years, a significant portion of the galaxy.

Imagine a future civilization using this technique to move their stars to better locations, or even rearranging huge portions of a galaxy for their own energy purposes.

This may sound theoretical, but Duncan Forgan, from the University of Edinburgh suggests a practical way to search for aliens moving their stars.

According to him, you could use planet-hunting telescopes like Kepler to detect the bizarre light signatures we’d see from a Shkadov Thruster. There’s nothing in the laws of physics that says it can’t happen.

It’s fun to think about, and gives us another way that we could search for alien civilizations out there across the galaxy.

Charter

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For the last seven years, this site has coordinated its efforts with the Tau Zero Foundation, and now serves as the Foundation's news forum. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image: Marco Lorenzi).

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